1. Field of the Invention
The invention relates to the preparation of d- or d,l-amphetamines.
2. Description of Related Art
U.S. Pat. No. 6,399,828 identifies two prior art techniques for synthesizing amphetamine from norephedrine.
In one approach, norephedrine first is refluxed with hydrogen iodide and red phosphorus. In the other approach, norephedrine is chlorinated using thionyl chloride and then the chlorinated product, following recrystallization from a methanol-isopropyl ether solution, is subjected to hydrogenolysis (catalytic hydrogenation) over a palladium-on-carbon catalyst.
Tomie et al., Chem. Pharm. Bull., Vol. 24, No. 5, pp. 1033-1039 (1976) describes a synthesis of threo-2-amino-1-chloro-1-phenylpropane from norephedrine by reaction with thionyl chloride in chloroform (trichloromethane —CHCl3). Following in vacuo concentration and an ether wash, the product was recrystallized from an ethanol solution.
Knie{hacek over (z)}o et al., Collection Czechoslovak Chem. Commun., Vol. 46, No. 3, pp. 717-724 (1981) describes a synthesis of threo-1-chloro-1-phenyl-2-propylammonium chloride from norephedrine by reaction with thionyl chloride in benzene (C6H6). Following vacuum concentration (“the mixture was taken down”), the product was recrystallized from an ethanol solution.
Workers continue to look for improved ways of making amphetamines, such as from phenylpropanolamines, such as norephedrine.